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The reciprocal of permeability is magnetic reluctivity. In SI units, permeability is measured in henries per meter (H/m), or equivalently in newtons per ampere squared (N/A 2). The permeability constant μ 0, also known as the magnetic constant or the permeability of free space, is the proportionality between magnetic induction and magnetizing ...
Using SI units, the magnetic induction B is related to H by the relationship = (+) = (+) =, where μ 0 is the vacuum permeability (see table of physical constants), and (1 + χ v) is the relative permeability of the material.
A practical unit for permeability is the darcy (d), or more commonly the millidarcy (md) (1 d ≈ 10 −12 m 2). The name honors the French Engineer Henry Darcy who first described the flow of water through sand filters for potable water supply. Permeability values for most materials commonly range typically from a fraction to several thousand ...
The vacuum magnetic permeability (variously vacuum permeability, permeability of free space, permeability of vacuum, magnetic constant) is the magnetic permeability in a classical vacuum. It is a physical constant , conventionally written as μ 0 (pronounced "mu nought" or "mu zero").
Rock permeability is usually expressed in millidarcys (md) because rocks hosting hydrocarbon or water accumulations typically exhibit permeability ranging from 5 to 500 md. The odd combination of units comes from Darcy's original studies of water flow through columns of sand. Water has a viscosity of 1.0019 cP at about room temperature.
In electromagnetism, permeance is the inverse of reluctance.In a magnetic circuit, permeance is a measure of the quantity of magnetic flux for a number of current-turns. A magnetic circuit almost acts as though the flux is conducted, therefore permeance is larger for large cross-sections of a material and smaller for smaller cross section lengths.
Unit name Symbol Base units E energy: joule: J = C⋅V = W⋅s kg⋅m 2 ⋅s −2: Q electric charge: coulomb: C A⋅s I electric current: ampere: A = C/s = W/V A J electric current density: ampere per square metre A/m 2: A⋅m −2: U, ΔV; Δϕ; E, ξ potential difference; voltage; electromotive force: volt: V = J/C kg⋅m 2 ⋅s −3 ⋅A ...
Weber (unit of magnetic flux) — The weber is the magnetic flux that, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second. [3] That is: =.